The present invention relates to coal feeders, and more particularly, to spider rotary coal feeders which are used to deliver a set quantity of coal over a given time period.
Raw coal feeders are typically be equipped with a hopper which is filled with coal. As the spider rotates, coal is fed into a compartment between two blades of the spider. It should be noted that this invention is equally applicable to other types of solid fuels or coarse particulate matter which fill compartments in a spider device. As the spider rotates, the coal in filled compartments drops by gravity to unload into an exit chute, the rate of fuel feed being determined by the size of the compartments and the speed of rotation of the spider.
Since the raw coal feeder just described is basically a metered feed device, it may be used to feed known quantities of fuel via a conveyor belt to a drying oven. The coal is then dried so as to improve the combustion of the coal which is eventually fed into a furnace.
When a raw coal feeder is used to deliver coal to a drying oven, it is desireable to preheat the coal prior to oven heating since this will help to prevent agglomeration of the coal. In addition, such drying will reduce the heat necessary in the drying oven stage of the coal feeding cycle to a furnace.
In the past, rotary devices have been used to feed fuel to furnaces. However, prior inventors have not been concerned with drying and heat which is generated and transmitted to a rotor device. U.S. Pat. No. 4,013,060 to Martin discloses a rotary grate with a partially hollow core which admits air into the core so that the air could flow through apertures of the cylindrical wall to contact the fuel. In this device, the air flow is used to cool the parts of the rotary grate. U.S. Pat. No. 1,433,109, to Brown discloses a spider rotary feed with cooling water circulating through an outer shell so as to disipate the heat cause by the friction of the blades of the spider against the casing. To the contrary, in the present device heated gas or air circulation is used to warm and dry the coal.
One objective of this invention is to provide a rotary coal feeder wherein coal which is being fed is heated before it leaves the rotary coal feeder.
A further objective of this invention is to heat the air found in the rotary spider compartments before it comes into contact with the coal.
A further objective of this invention is to minimize agglomeration of coal which leaves a rotary feeder.
A further objective of this invention is to avoid coal becoming stuck to the blades of a rotary coal feeder.
Further objectives will become apparent from the specification wherein a preferred embodiment is disclosed by way of example and not of limitations as shown by the attached drawings.